The code is perhaps the least-referenced open-source S3 gateway package, and from a vanilla RHEL 7.3 build we had to add a significant number of packages to get to the utility compiled and installed.
S3QL is written in Python.
Significant additions are required to build S3QL namely: llfuse, Python3, Cython, Python-pip, EPEL and SQlite.

S3QL uses the Python bindings (llfuse) to the Linux user-mode kernel FUSE layer.
By default, it uses the POSIX handle mapped as an S3 object in a one-to-one map.
S3QL supports only one node sharing one subset (directory) tree of one S3 bucket.
There is no sharing in this model.

Several code exception/faults were seen in Python subroutines of the
mkfs.s3ql utility during initial test so, due to time pressures, we
will revisit this later.

Although the process exceptions are probably due to a build error, and plainly the product does work, this does highlight that the build process was unusually complex, due to the nature of so many dependencies on other open-source components.
This may play as a factor in the decision process for selecting solutions.